In the related art, a machine tool including a spindle supported by a bearing is used. In this machine tool, various machining with respect to a work piece is performed by relatively moving a tool attached to the spindle and the work piece. In this way, when the tool attached to the spindle and the work piece relatively move toward each other, due to input errors of a Numerical Control (NC) program defining a movement direction or an amount of movement of the tool or the work piece, or operation errors of an operator, the spindle, the tool, the work piece or the like collides with each other, and thus, the machine tool may be damaged.
Accordingly, a control device of a machine tool for determining a degree of damage to a machine tool due to a collision and for determining whether or not it is necessary to exchange parts of a machine is suggested. For example, in a control device of a machine tool disclosed in PTL 1, when a table or a load on the table collides with a spindle or the like while the machine tool is operated, a magnitude of impact with respect to a ball screw is determined by calculating a load of collision applied to the ball screw driving the table and comparing the calculated load and the reference value set in advance.